Drawing instrument



W. THOMPSON ET AL DRAWINQ; INSTRUMENT Filed Dec. 10. 1925 l I I] p 1, =57 F1 INVENTORS William Thompson 3: Gilbert Marsh By their Attorne SPatented Oct. 5, 1926.

UNITED STAT ES WILLIAM THOMPSON AND GILBERT MARSH, BRIGHTON, ENGLAND.

' DRAWING INSTRUMENT.

Application filed December llipsographs and like instruments com monl)comprise a frame having two grooves at right angles to one another, aslide in each groove and an arm carrying a pencil or the like pivoted toboth slides.

According to this invention an ellipsograph or the like is formed of twogrooved rules, one of which is arranged to slide on the other, whereby aportion of an ellipse or an arc of a circle can be drawn and combinedwith a portion of another ellipse or an arc of a circle. The pivotedmembers on the slides carrying the pencil arm are such that the arm canslide therein but can be rendered fast therewith.

In one method of carrying out the invention, an instrument comprises twofixed grooved rules at right angles to each other and a slidable groovedrule, while the slides are provided with means for rendering one orother slide fast in its groove, whereby other curves can be drawn withthe instrument.

In the accompanying drawings which i1- lustrate the invention, Figure 1is a plan, Figure 2 a detail plan of a slide, Figure 3 a detail plan ofa second slide, Figure 4 a section on the line IVIV, Figure 1, andFigure 5 a detail elevation.

1, 2, are slides pivotally mounted on each of which is a guide 3, withinwhich is loosely mounted a block 4, the said block being provided with ascrew 5 which passes through the guide 3 and is provided with a lockingring 6. Each guide 3 and block 4 is slotted at 7, 8, respectively, whilethe guide 3 is provided with a pointer 9, and each slide 1, 2, isprovided with a pointer 10. The slides 1, 2, are provided with rollers11 which are adapted to run on tracks 12 formed on rules 13, 14, mountedat right angles to each other, while grooves 15 formed in the said rulesare engaged by the slides 1, 2. The slides 1, 2, are each provided witha locking screw 16 which, when in the locking position, bear upon thetracks 12. 17 is a third rule which is adapted to slide upon either ofthe rules 13, 14, the said rule 17 being also provided with a track 12,and with grooves 15. The rule 17 is provided with a locking screw 18. 19is an arm which is adapted to pass through the slots 7, 8, in the guides3, and the blocks 4, the said arm being provided at one end with amarking instrument, such as a pencil 20, or with a cutting instrument,such as a diamond for cutting glass, and

10, 1925. SerialNo. 74,585.

with arod 21 between a pin 22 on which and the'arm 19 is interposed aspring 23, the rod 21 and spring 23 serving to relieve the pencil orcutting instrument of a portion of the weight of the arm 19. The outerextremity of each rule 13, 14, is provided with means, such as thesockets 24, which are adapted to receive plugs 25 on extensions 26whereby the length of the rules 13, 14, may if desired be increased. Therules 13, 14, and 17, and the arm 19 may be marked with the Englishsystem of linear measurement on one side, and on the other side with themetric system, the reading being made against the pointers 9, 10.

In operation, when for example it is desired to form a curve of theelliptic-Gothic type, the elliptic portion A-B on each side of thecentre line of the curve is formed by allowing the slides 1, 2, to movefreely along the rules 13, 14, (as shown in dotted lines in Figure 1),the arm 19 having been set in the desired position and prevented frommoving longitudinally relatively to the said slides by the locking rings6. The portion C-D (i. e. the Gothic portion) is produced by removingthe slide 1 from the rule 13 and sliding it upon the rule 17 (which islocked in the desired position by the screw 18) until the desiredposition is reached (as shown in full lines in Figure 1), whereupon thesaid slide is locked by its locking screw 16. The arm 19 is then slidthrough the slotted portions 7, 8, of the guide 3 and block 4 and lockedby the ring 6 when the desired position is reached. The portion C-D isthen produced. The slide 1 is then placed upon the other sideof the rule17 and the Gothic portion E-F of the curve produced, whereby a completeelliptic-Gothic curve is obtained.

It is obvious that the instrument may be employed for other curves, suchas true elliptical curves, in which case movement of the slides 1, 2, inthe rules 13, 14, is completed. v

The instrument may also be used as a beam compass by fixing one of theslides 1, 2.

WVhat we claim is 1.. In a drawing instrument, the combination of a pairof rules at right angles to each other, a third rule adapted to slide oneither of said first mentioned rules, slides adapted to slide on any ofsaid rules, pivotal members on said slides, an arm adapted to slide insaid pivotal members, means adapted. to

render said arm fast With any of said pivotal members, and means formarking or cutting carried by said arm.

2. In a drawing instrument, the combina tion of a pair of rules at rightangles to each other, a third rule adapted to slide on said firstmentioned rules, means for rendering fast said third rule to the one ofthe first mentioned rules on which it is positioned, slides adapted toslide on said rules, means for rendering fast said slides to any of saidrules, pivotal members on said slides, an arm adapted to slide in saidpivotal members, leans adapted to renoer said arm fast with any of saidpivotal members, and means for marking or cutting carried by said arm.

In testimony that We claim the foregoing as our invention, We havesigned our names this first day of December, 1925.

lVILLIAM THOMPSON. GILBERT MARSH.

